Everything has its place.
You basically 'at your valve lifts' gained 6-8 cfm. That's a days work most would rather watch for free. Lol
The real test....put the other heads back on, change the cam and the rest, gear, convertor...run it...then swap heads.
It has to be apples to apples... not apples to caramel dipped apples.
What do they add, same cam and everything when used in their 'sweet spot'